Should You Lime When Overseeding?

Overseeded lawns require regular irrigation.

Since warm-season grasses turn dormant and brown in the winter, annual ryegrass (Lolium multiflorum) is often overseeded in the fall to provide winter color. Fall is also the best time to apply lime, so overseeding and lime application happen around the same time. Lime should not be applied every year, however, since this can make the soil too alkaline for turf grass.

Understanding Soil pH

How much lime to apply is largely determined by the pH of the soil. The pH is expressed on a scale between 1.0 and 14. A neutral pH is 7.0. Numbers lower than 7.0 refer to acidic conditions, and numbers higher than 7.0 are alkaline. Lawn grasses grow best when the soil pH is between 5.5 and 7.0. Soil becomes more acidic over time due to leaching of calcium and magnesium from the soil, as well as applications of nitrogen fertilizers and organic matter like compost. The application of lime raises soil pH to correct these problems.

How Much Lime?

Home pH tests show soil pH and whether lime is required, but only a test run by a soil-testing laboratory can determine exact application rates for lime. The soil test report will indicate how much lime is needed by giving a rate of pure calcium carbonate required per 1,000 square feet. Individual liming products vary in how much calcium carbonate they contain. For example, dolomitic, pelletized and ground limestone contain 70 to 95 percent calcium carbonate. The maximum application rate for these sources of lime is 50 pounds per 1,000 square feet.

Timing Lime with Overseeding

Lime can be applied to established lawns at any time of the year, as long as the grass is not wilted or covered with frost. However, fall applications are best so that winter rains can help move lime down into the soil. Therefore, the use of lime often coincides with overseeding warm-season grass. Unlike overseeding, lime applications are not performed every year. A yearly soil test can be used to determine how frequently lime is needed, but in general, lime is only applied every three to five years.

Tips for Overseeding Lawns

Overseeding annual ryegrass is best done two weeks before the first frost or when soil temperatures reach 65 to 70 degrees Fahrenheit. If using lime, apply before seeding. To prepare the lawn for seeding, dethatch with a vertical mower or dethatching hand rake. Spread seed evenly across the lawn at a rate of 10 pounds per 1,000 square feet. Lightly water twice a day until the seed germinates. Once it is tall enough, mow ryegrass just like a regular lawn. It will grow alongside the permanent lawn until spring when the weather becomes warm enough to bring the warm-season grass out of dormancy and kill the ryegrass.

About the Author

After graduating from The Ohio State University, Marissa Baker turned her attention to professional writing. Her experience covers a variety of topics, including gardening, landscaping and lawn care equipment. She has been gardening for as long as she can remember, and writing about garden and lawn care since 2012.